Nephilim are the very rare crossing of a Non-magical race with a Celestial. Unlike Lilin (which are much more common) Nephilim are almost always the result of Celestial ancestory many generations ago asserting itself. As such, a Nephilim is considered a blessing to their family and community, as if it were a gift from Veza herself.
Unlike other hybrids, Nephilim tend to look like whatever their Non-magical race is, though perhaps a bit taller in the case of gnomish or dwarven Nephilim. Because of this, some Nephilim may go a long time into adulthood without realizing what they are. It's even possible they don't realize it until it becomes clear they've stopped aging while those around them have continued.
Much like Celestials, Nephilim have a 'default form', however this is highly dependant on the individual. For most, it's simply their idealized self, with angelic wings. But this form has a lot to do with what the individual believes a Nephilim looks like. For those who discover themselves later in life, it may just be their 'normal' self. For others, it might be closer to the appearance of a true Celestial. (The only limit on this form is the limit on the Nephilim's shape-shifting ability.)
Nephilim have very similar, though lessened forms of the abilites of their Celestial ancestors. (It's believed that this has cause some Nephilim to impersonate Celestials in order to be worshiped, though a specific case has never been found.)
Unlike Celestials, however, Nephilim power their magical abilities with the Living Force of themselves and those around them. (This has an interesting effect of allowing a Nephilim to replenish their magic by defending or leading a large group of people from which they can passively drain Living Force.) Nephilim have an amount of magic that they can store and use. With practice and training they can increase this, but unlike magical creatures, [Dragonborn][] or even monsters, they have a limited amount of magic that they have to replenish.
Nephilim can fly much in the same way Celestials can, however, their flight duration is limited by how much magical energy they've stored up. It takes quite a bit of magical energy to fly.
Most of the shape-shifting Nephilim do is subconscious. They can generally produce wings without much effort (though sometimes removing them can be difficult until they get used to it). With practice, they can make changes to their physical appearance and gain a portion of a Celestial's abilities.
Nephilim can't change their shape to be too different from their 'default form'. They must remain humanoid (so they can't shift into becoming a dragon, though looking like a dragonborn would be possible). Whenever a Nephilim looses consciousness, they will revert to their default form.
Note: Because a Nephilim's default form is their perfected self, this can lead to a very awkward situation in which once they fall asleep they look much different from when they are wake. If this is before they realize they are a Nephilim, sometimes it can be others in their lives who learn this fact before they do.
Nephilim are not, technically immortal. They have a high resistances to disease and they stop aging much like their Celestial ancestors, however they are far less resiliant than Celestials. What's more, they seem to start aging again after their races normal lifespan, albeit slowly. It's hard to tell if this is actual aging, or more of thier own perception of themself changing as they feel they should age.
That being said, Nephilim are decidely mortal. How and why they die is different for each, but they are all destined to die.
Nephilim are much more effected by their own personal beliefs than their Celestial ancestors. If they believe themselves to be powerless, they will actually lose their powers. Because of this, their abilities are greatly limited by what they believe their own limitations to be.
Nephilim are rare enough that almost all of them have become well known heros throughout history. But because of how rare they are, they've never formed their own culture. In fact, they happen so rarely, most have to figure out what they are and how they work on their own. It's entirely possible that there have been many more Nephilim than what are known, but they didn't even know themselves.
In general, the Non-magical races view Nephilim as devine heros and warriors for the Goddess Veza (despite their powers being magical in nature).
This is what it means to be a true hero. I've never met one, but I used to read all about them when I was a kid, and they're the most genuine heros I've ever heard of. I hope I'll get to meet one, eventually.
Having met two, I can say that the heroism and strength is not overestimated. They are exactly what everyone wishes them to be. But, they are also mortal, a fact that we sadly forget in our ferver.
True heros, the lot of 'em. Wish there were more dwarves among their ranks, but not gunna take issue with them about that, now am I?
If their deeds are anything to go by, they're honorable, skilled warriors. But no man or woman is just their deeds, so I've always wondered... who, exactly, were these heros we all worship? And more to the point, what makes them any different from the Lilim, in the end? I'd be cautious about putting to much faith into these beings.
Oh. Yes, well. The Nephilim certainly are something. What? No, nothing's wrong. It's just... perhaps we don't need any more tragic heros? Maybe the next time a Nephilim comes along we let them do something more mundane, like farming? ...No, nevermind. It's a silly idea.
The Magical races are a bit less fond of Nephilim than their Non-magical counterparts, knowing that for all the good they've done there's been just as many bad apples.
The power to inspire is a double edged blade. You can push others to heights they never would have reached on their own, and yet, when you fall, you take everyone else down with you.
Our offspring have much to learn. They continue to impress us, but we wish we could provide more direct guidance. So many loose their way, it's sad to see.
My mother told me that if I've got nothing nice to say, I shouldn't say anything at all... where other people can hear. Let's just go with 'not a fan'.
They seem so focused on 'making a difference' they fail to ask the more fundamental question: does a difference even need to be made? They would do better to not take on the world burdens without asking.